The present invention relates to a fiber composition containing a phase change material integrally incorporated into the structure of a fiber forming polymer. The fiber composition is then useful in textile materials, in general, and in clothing, in particular.
Phase change materials may be repeatedly converted between solid and liquid phases to utilize their latent heat of fusion to absorb, store and release heat or cool during such phase conversions. These latent heats of fusion are greater than the sensible heat capacities of the materials. For example, in phase change materials, the amount of energy absorbed upon melting or released upon freezing is much greater than the amount of energy absorbed or released upon increasing or decreasing the temperature of the material over an increment of 10.degree. C.
Upon melting and freezing, a phase change material absorbs and releases substantially more energy per unit weight than a sensible heat storage material that is heated or cooled over the same temperature range. In contrast to a sensible heat storage material which absorbs and releases energy essentially uniformly over a broad temperature range, a phase change material absorbs and releases a large quantity of energy in the vicinity of its melting/freezing point.
Phase change materials have been used in a variety of applications. They have been included in wall and floor boards to store heat to provide a room with a comfortable ambient temperature. They have also been incorporated into cups, glasses and tableware to keep foods and beverages at a desired eating temperature for extended periods of time.
Phase change materials have also been used to keep clothing at a comfortable temperature. One application requires the use of alkyl hydrocarbons mixed with silicon dry powders contained in plastic film pouches which are placed between layers of clothing. See e.g. Salyer, U.S. Pat. No. 5,211,949 issued May 18, 1993 and assigned to the same assignee as the present invention. The pouches are bulky and only provide a benefit to those areas of the article of clothing in which the pouch is used. The shape of these pouches makes it difficult to secure them throughout a garment. Phase change materials have also been microencapsulated for use in clothing applications. However, the microcapsules do not have the structural integrity to withstand the force exerted on the microcapsule when the encapsulated phase change material is extruded to form fibers. Others have attempted to coat a phase change material onto textile fibers but this application does not permit the use of a sufficient amount of the phase change material to provide effective phase change properties in the article of clothing formed from these coated fibers.
Thus, a need has arisen in the art for a fiber which successfully incorporates a phase change material to provide an article of clothing or bedding having comfortable properties produced by the phase change materials.